1. Field of the Invention.
The present invention relates generally to a satellite broadcast system, and in particular, to optimizing transmitter uplink power efficiency for such a satellite broadcast system.
2. Description of the Related Art.
Satellite broadcasting of communications signals has become commonplace. Satellite distribution of commercial signals for use in television programming currently utilizes multiple feedhorns on a single Outdoor Unit (ODU) which supply signals to several Integrated Receiver & Decoders (IRDs) on separate cables from a multiswitch.
FIG. 1 illustrates an example satellite television broadcast system of the related art.
System 100 uses signals sent from Satellite A (SatA) 102, Satellite B (SatB) 104, and Satellite C (SatC) 106 (with transponders 28, 30, and 32 converted to transponders 8, 10, and 12, respectively), that are directly broadcast to an Outdoor Unit (ODU) 108 that is typically attached to the outside of a house 110. ODU 108 receives these signals and sends the received signals to IRD 112, which decodes the signals and separates the signals into viewer channels, which are then passed to television 114 for viewing by a user. There can be more than one satellite transmitting from each orbital location.
Satellite uplink signals 116 are transmitted by one or more uplink facilities 118 to the satellites 102-106 that are typically in geosynchronous orbit. Satellites 102-106 amplify and rebroadcast the uplink signals 116, through transponders located on the satellite, as downlink signals 120. Depending on the satellite 102-106 antenna pattern, the downlink signals 120 are directed towards geographic areas for reception by the ODU 108.
Each satellite 102-106 broadcasts downlink signals 120 in typically thirty-two (32) different sets of frequencies, often referred to as transponders, which are licensed to various users for broadcasting of programming, which can be audio, video, or data signals, or any combination. These signals have typically been located in the Ku-band Fixed Satellite Service (FSS) and Broadcast Satellite Service (BSS) bands of frequencies in the 10-13 GHz range. Other satellites may also broadcast in a portion of the Ka-band with frequencies of 18-21 GHz. Alternatively, signals can be transmitted in series or in parallel via cable 122 to IRD 112.
The uplink signals 116 power is limited and frequency allocations are fixed in size and, thus, the power and bandwidth for transmission in those frequency bands limit the ability of the system 100 to transmit additional signals using the current transmission and receiving method. With additional satellites and additional channels, more signals must be transmitted within the power and bandwidth constraints to allow for additional programming within system 100.
It can be seen, then, that there is a need in the art for a satellite broadcast system to increase the power and spectral efficiency with the allocated bandwidth.